alkénem

Alkenes are a class of unsaturated hydrocarbons characterized by the presence of at least one carbon-carbon double bond. Their general formula is CnH2n, where n is an integer representing the number of carbon atoms. The simplest alkene is ethene (C2H4), followed by propene (C3H6) and butene (C4H8). The double bond consists of one sigma bond and one pi bond. The pi bond is weaker than the sigma bond and is the site of most alkene reactions.

Alkenes are generally less reactive than alkanes due to the presence of the double bond. However, they undergo a variety of addition reactions, where atoms or groups of atoms are added across the double bond. Common addition reactions include hydrogenation (addition of hydrogen), halogenation (addition of halogens like chlorine or bromine), hydrohalogenation (addition of hydrogen halides like HCl or HBr), and hydration (addition of water). These reactions typically break the pi bond, forming a single bond between the carbon atoms and introducing new atoms or groups.

Alkenes are important in organic chemistry and industry. Ethene, for example, is a major feedstock for the production of polyethylene, one of the most widely used plastics. Propene is used to produce polypropylene, another important plastic. Alkenes also serve as starting materials for the synthesis of many other organic compounds, including alcohols, ethers, and epoxides. Their reactivity makes them versatile building blocks in chemical synthesis.